i think the grill is recessed in the mid range section, to give the a more "design" look, that just a flat grill... i would bet Ian and andrew used the injection molding machine to get the backing to get the correct geometry, then stretch/glue the cloth material to the form.

That's what I thought. You can now have different grill configurations depending on your mood. Maybe even different colour options for the segments? I don't think I've ever seen a speaker with three different colours on the front.